The present invention relates to film/foil laminates, and in particular film/foil laminates wherein a plurality of metal sheets and polymeric films are bonded together.
In the past, various combinations of metallic sheets with non-metallic coatings, substrates and the like have been employed to provide a packaging material, or to alter the inherent properties of metallic sheets.
U.S. Pat. No. 4,211,822 (Kurfman et al) discloses a layer of polystyrene or polycarbonate film metallized with indium or tin/cadmium alloy. This results in reflective and decorative parts for automobiles and other vehicles. The polymer may be pretreated including the use of corona discharge. Materials such as polyvinyl halide or polyvinylidene halide are disclosed as polymers of the polymer layer. The metal layer may be applied to both sides of the polymer layer.
U.S. Pat. No. 4,241,129 (Marton et al) discloses a multilayer metal/organic polymer like that of the Kurfman patent, and including a soft adhesive polymer such as ethylene vinyl acetate copolymer.
U.S. Pat. No. 4,257,536 (Hilmar et al) discloses a laminate structure for dispensing containers having an aluminum layer bonded to a corona treated polyester barrier layer by a polyester or other suitable adhesive layer.
U.S. Pat. No. 4,291,085 (Ito et al) discloses a polypropylene layer which has been corona treated, bonded to a layer of aluminum foil.
U.S. Pat. No. 4,528,234 (Kaiho et al) discloses an aluminum layer bonded to a corona bonded plastic substrate.
U.S. Pat. No. 4,597,818 (Aoyama et al) discloses an aluminum substrate bonded to a corona treated ultra-high molecular weight polyethylene.
U.S. Pat. No. 4,749,625 (Obayashi et al) discloses an amorphous metal with a polymeric coating layer laminated to one surface of the amorphous metal.
U.S. Pat. No. 4,766,035 (Lancaster et al) discloses a metal substrate with a halopolymer adhered thereto.
U.S. Pat. No. 4,855,186 (Grolig et al) discloses a plastic carrier film, a first dielectric layer adhered to the carrier film, and a heat reflection metallic layer adhered to the first dielectric layer.
WO 82/00020 (Nelson-Ashley et al) discloses adhering a linear low density polyethylene film to a sheet metal or foil by engaging the film and sheet metal, heating at least the sheet metal, and applying pressure to the opposed free surfaces. This article may be folded to a pouch.
French Patent Abstract No. FR 2618382-A discloses a packaging material comprising a heat shrinkable plastics material layer adhered to a layer of metallic, preferably aluminum foil. The preferred heat shrinkable layer is polyethylene.
Japanese Patent No. J01027923-A (Mitsui) discloses coextrusion-laminating a resin layer to an oriented film or an aluminum foil through an adhesive layer. The resin may be a polyolefin.
UK Patent Specification 1295132 discloses the pretreatment of one surface of a plastic film by corona discharge; bringing the treated film into contact with a steel sheet at a temperature sufficient to soften the plastic film; and annealing the plastic/metal laminate at or above the melting point of the plastic.
A problem associated with some conventional film/foil laminate is that it is subject to pin holes and flex cracks. When this occurs, the gas barrier properties of the laminate is degraded, sometimes to such an extent that the laminate loses its utility for the intended end use.
It has now been discovered that by providing a multiplicity of polymeric films and foils laminated together, a laminate is produced which approaches an absolute barrier.
This laminate can be made into for example a vacuum insulating panel by making a pouch, filling it with a separating material (such as a non-woven material or silica), evacuating the pouch and sealing it.
An additional advantage of the present invention is that different metal foils can be combined into a coherent stampable sheet. Therefore metal such as aluminum and steel can be used and built up in thickness to achieve a laminate sheet capable of being stamped or shaped as desired, e.g. beverage cans.